/*
 * @Author: Clark
 * @Email: haixuanwoTxh@gmail.com
 * @Date: 2023-01-13 15:53:26
 * @LastEditors: Clark
 * @LastEditTime: 2023-01-13 16:02:14
 * @Description: file content
 */

#include "apue.h"
static void sig_quit(int);

int main()
{
    sigset_t newmask, oldmask, pendmask;
    if (signal(SIGQUIT, sig_quit) == SIG_ERR)
    {
        err_sys("can't catch SIGQUIT");
    }

    sigemptyset(&newmask);
    sigaddset(&newmask, SIGQUIT);
    if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
    {
        err_sys("SIG_BLOCK error");
    }

    sleep(5);
    if (sigpending(&pendmask) < 0)
    {
        err_sys("sigpending error");
    }

    if (sigismember(&pendmask, SIGQUIT))
    {
        printf("\nSIGQUIT pending\n");
    }

    if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
    {
        err_sys("SIG_SETMASK error");
    }
    printf("SIGQUIT unblocked\n");

    sleep(5);
    exit(0);
}

static void sig_quit(int signo)
{
    printf("caught SIGQUIT\n");
    if (signal(SIGQUIT, SIG_DFL) == SIG_ERR)
    {
        err_sys("can't reset SIGQUIT");
    }
}
